Metal hard mask for precise tuning of mandrels

Abstract

A method of forming a mandrel for use in a pitch doubling process is provided in which a metal hard mask is inserted between a mandrel material layer and a soft mask. The insertion of the metal hard mask allows for easier pattern transfer into the mandrel material layer and avoids many issues encountered during multi-patterning steps. The insertion of the metal hard mask forms a square mandrel that has a flat top due to durability against etch and ability to wet strip the metal hard mask. The metal hard mask can be tuned before pattern transfer into the underlying mandrel material layer to provide a hard mask pattern that is smaller or larger than the pattern without performing such tuning. The method also can be used to protect the downstream non-mandrel processes where selectivity is crucial.

What is claimed is: 
     
       1. A method of forming a structure, the method comprising:
 forming a mandrel patterning material stack on a mandrel material layer that is located above at least one material layer, wherein the mandrel patterning material stack comprises a metal-containing hard mask layer in direct physical contact with the mandrel material layer and an organic containing soft mask material layer located above the metal-containing hard mask layer; 
 first patterning the mandrel patterning material stack to provide a plurality of metal-containing hard masks and a plurality of organic containing soft masks; and 
 second patterning the mandrel material layer utilizing the metal-containing hard masks as etch masks so as to provide a plurality of mandrels, wherein the mandrels have a pitch that is less than 36 nm. 
 
     
     
       2. The method of  claim 1 , wherein the at least one material layer is present in a back-end-of-the-line (BEOL) region of a semiconductor structure. 
     
     
       3. The method of  claim 1 , wherein the at least one material layer is a dielectric material, an electrically conductive material or any combination thereof. 
     
     
       4. The method of  claim 1 , wherein the pitch of the mandrels is from 26 nm to 35 nm. 
     
     
       5. The method of  claim 1 , wherein each of the metal-containing hard masks has a first lateral width, and the method further comprises tuning the first lateral width to a second lateral width that is different from the first lateral width. 
     
     
       6. The method of  claim 5 , wherein the first lateral width is greater than the second lateral width, and the tuning comprises shrinking the first lateral width utilizing an etching process that removes a portion of each of the metal-containing hard masks. 
     
     
       7. The method of  claim 5 , wherein the first lateral width is less than the second lateral width, and the tuning comprises forming a metal spacer along a sidewall of each of the metal-containing hard masks. 
     
     
       8. The method of  claim 1 , further comprising forming one or more mandrel underlying masking layers between the mandrel material layer and the at least one material layer. 
     
     
       9. The method of  claim 1 , wherein the first patterning of the mandrel patterning material stack comprises:
 forming a patterned photoresist on top of the mandrel patterning material stack, the patterned photoresist having a mandrel pattern; and 
 transferring the mandrel pattern into the organic containing soft mask material layer and the metal-containing hard mask layer of the mandrel patterning material stack by etching so as to provide the plurality of organic containing soft masks and the plurality of metal-containing hard masks, respectively. 
 
     
     
       10. The method of  claim 9 , wherein the plurality of organic containing soft masks are removed prior to the patterning of the mandrel material layer. 
     
     
       11. The method of  claim 9 , wherein the mandrel patterning material stack further comprises a dielectric oxide layer located between the metal-containing hard mask layer and the organic containing soft mask material layer, wherein the dielectric oxide layer is converted to a plurality of dielectric oxide masks during the transferring of the mandrel pattern. 
     
     
       12. The method of  claim 11 , wherein the metal-containing hard mask layer is composed of titanium nitride, the dielectric oxide layer is composed of silicon dioxide, the organic containing soft mask material layer is composed of an organic planarization layer material, and the mandrel material layer is composed of silicon nitride. 
     
     
       13. The method of  claim 1 , further comprising forming a mandrel pitch doubling spacer along sidewalls of each of the mandrels and each of the metal-containing hard masks. 
     
     
       14. A method of forming a structure, the method comprising:
 forming a mandrel patterning material stack on a mandrel material layer that is located above at least one material layer that is present in a back-end-of-the-line (BEOL) region of a semiconductor structure, wherein the at least one material layer is a dielectric material, an electrically conductive material or any combination thereof, and wherein the mandrel patterning material stack comprises a metal-containing hard mask layer in direct physical contact with the mandrel material layer and an organic containing soft mask material layer located above the metal-containing hard mask layer; 
 first patterning the mandrel patterning material stack to provide a plurality of metal-containing hard masks and a plurality of organic containing soft masks; and 
 second patterning the mandrel material layer utilizing the metal-containing hard masks as etch masks so as to provide a plurality of mandrels having a pitch from 26 nm to 64 nm. 
 
     
     
       15. The method of  claim 14 , wherein each of the metal-containing hard masks has a first lateral width, and the method further comprises tuning the first lateral width to a second lateral width that is different from the first lateral width. 
     
     
       16. The method of  claim 15 , wherein the first lateral width is greater than the second lateral width, and the tuning comprises shrinking the first lateral width utilizing an etching process that removes a portion of each of the metal-containing hard masks. 
     
     
       17. The method of  claim 15 , wherein the first lateral width is less than the second lateral width, and the tuning comprises forming a metal spacer along a sidewall of each of the metal-containing hard masks. 
     
     
       18. The method of  claim 14 , further comprising forming one or more mandrel underlying masking layers between the mandrel material layer and the at least one material layer. 
     
     
       19. The method of  claim 14 ,
 wherein the first patterning of the mandrel patterning material stack comprises: 
 forming a patterned photoresist on top of the mandrel patterning material stack, the patterned photoresist having a mandrel pattern; and 
 transferring the mandrel pattern into the organic containing soft mask material layer and the metal-containing hard mask layer of the mandrel patterning material stack by etching so as to provide the plurality of organic containing soft masks and the plurality of metal-containing hard masks, respectively. 
 
     
     
       20. The method of  claim 19 , wherein the plurality of organic containing soft masks are removed prior to the patterning of the mandrel material layer. 
     
     
       21. The method of  claim 19 , wherein the mandrel patterning material stack further comprises a dielectric oxide layer located between the metal-containing mask layer and the organic containing soft mask material layer, wherein the dielectric oxide layer is converted to a plurality of dielectric oxide masks during the transferring of the mandrel pattern. 
     
     
       22. The method of  claim 21 , wherein the metal-containing hard mask layer is composed of titanium nitride, the dielectric oxide layer is composed of silicon dioxide, the organic containing soft mask material layer is composed of an organic planarization layer material, and the mandrel material layer is composed of silicon nitride. 
     
     
       23. The method of  claim 14 , further comprising forming a mandrel pitch doubling spacer along sidewalls of each of the mandrels and each of the metal-containing hard masks. 
     
     
       24. A method of forming a semiconductor structure, the method comprising:
 forming a mandrel patterning material stack on a mandrel material layer that is located above a material layer, wherein the mandrel patterning material stack comprises a metal-containing hard mask layer in direct physical contact with the mandrel layer and an organic containing soft mask material layer located above the metal-containing hard mask layer; 
 first patterning the mandrel patterning material stack to provide a plurality of metal-containing hard masks and a plurality of organic containing soft masks; 
 shrinking the first lateral width of each of the metal-containing hard masks to a second lateral width by etching; and 
 second patterning the mandrel material layer utilizing the metal-containing hard masks having the second lateral width as etch masks so as to provide a plurality of mandrels. 
 
     
     
       25. A method of forming a semiconductor structure, the method comprising:
 forming a mandrel patterning material stack on a mandrel material layer that is located above a material layer, wherein the mandrel patterning material stack comprises a metal-containing hard mask layer in direct physical contact with the mandrel layer and an organic containing soft mask material layer located above the metal-containing hard mask layer; 
 first patterning the mandrel patterning material stack to provide a plurality of metal-containing hard masks and a plurality of organic containing soft masks; 
 increasing the first lateral width of each of the metal-containing hard masks to a second lateral width by forming a metal spacer along a sidewall of each of the metal hard masks; and 
 second patterning the mandrel material layer utilizing the metal-containing hard masks having the second lateral width as etch masks so as to provide a plurality of mandrels.